Simply defragment it by right clicking your SD card icon and go on the tools tab, and then click Defragment. You could do Disk Check to for more recovery.
The best way to recover this is make a backup and copy all of your files (private, apps, codes, etc.) from your SD card into a folder like in your My Documents folder, and format everything in your SD card. It will delete everything in there, and you can simply copy all your files from your My Documents to your SD card.
The only reason why it changes songs because when you delete or manually/automatically move files, it leaves little leftovers in the folder, which causes a mix up of songs in-game. It even causes more problem, which makes a loud static-like noise, which is a mix up of most of the songs you deleted or moved.
